1. Field
The disclosed embodiments relate to video decoding.
2. Background Information
Cellular telephones provide their users more functionality than just an ability to make and receive wireless telephone calls. Cellular telephone manufacturers are incorporating more and more functionality into their cellular telephones in order to compete for user interest with other cellular telephone manufacturers. A cellular telephone manufacturer may, for example, build a video receiving capability into their cellular telephones. The cellular telephone is to be usable to receive a stream of compressed video information transmitted from a satellite, to decode the compressed information into video, and to display the video on the display of the cellular telephone. The cellular telephone user may therefore watch satellite television programming on the display of the cellular telephone. The manufacturer, however, also wants the cellular telephone to be inexpensive to manufacture. In one example, an older semiconductor processing technology is to be used to realize digital processing circuitry of the cellular telephone in order to reduce the cost of the integrated circuits making up the cellular telephone. Using the older processing technology is less expensive than using a higher speed, newer processing technology.
In one example, the older processing technology limits the clock speed of a digital signal processor that can be realized to about one hundred megahertz. It is desired to be able to use this older technology to video decode thirty frames per second of VGA (640×480 pixels) compressed video information, and to display the resulting VGA resolution video in real time on the display of the cellular telephone. Unfortunately, a one hundred megahertz digital signal processor does not have adequate throughput to carry out the required amount of processing. A digital signal processor having a clock frequency of 250 to 300 megahertz would be required to decode the VGA video stream at thirty frames per second. Accordingly, if the inexpensive semiconductor processing technology is used, then it may only be possible for the cellular telephone to display one third the desired resolution images at the desired thirty frames per second frame rate.
There also may be reasons other than cost for limiting the frequency of clock signal that clocks the digital signal processing circuitry within a cellular telephone.